Introducers and catheters have been in use for medical procedures for many years. For example, one use has been to convey an electrical stimulus to a selected location within the human body. Another use is the monitoring of measurements for diagnostic tests within the human body. Catheters may examine, diagnose and treat while positioned at a specific location within the body which is otherwise inaccessible without more invasive procedures. These catheters are then guided to a specific location for examination, diagnosis or treatment by manipulating the catheter through the artery or vein of the human body.
The utilization of the catheters is frequently limited because of the need for a precise placement of the electrodes of the catheter at the specific location within the body.
Control of the movement of catheters to achieve such precise placement is difficult because of the inherent structure of the catheter. The body of a conventional catheter is long and tubular. To provide sufficient control of the movement of the catheter, it is necessary that its structure be somewhat rigid. However, the catheter must not be so rigid as to prevent the bending or curving necessary for movement through the vein, artery or other body part to arrive at the specified location. Further, the catheter must not be so rigid as to cause damage to the artery or vein while it is being moved within the body.
It is also important that there be sufficient rigidity in the catheter to accommodate torque control, i.e., the ability to transmit a twisting force along the length of the catheter. Sufficient torque control enables controlled maneuverability of the catheter by the application of a twisting force at the proximal end of the catheter that is transmitted along the catheter to its distal end. The need for greater torque control often conflicts with the need for reduced rigidity to prevent injury to the body vessel.
Catheters are used increasingly for medical procedures involving the human heart. In these procedures a catheter is typically advanced to the heart through veins or arteries and then is positioned at a specified location within the heart. Typically, the catheter is inserted in an artery or vein in the leg, neck, upper chest or arm of the patient and threaded, generally with the aid of a guidewire or introducer, through the various arteries or veins until the distal tip of the catheter reaches the desired location in the heart.
The distal end of a catheter used in such a procedure is sometimes preformed into a desired curvature so that by torquing the catheter about its longitudinal axis, the catheter can be guided to the desired location within the heart or in the arteries or veins associated with the heart.
Catheter assemblies have also been designed wherein a catheter having a predetermined curve is received within a sheath that is advanced over the distal end of the catheter. Advancement of the catheter within the sheath modifies the predetermined curve of the distal end of the catheter. See U.S. Pat. Nos. 5,290,229, 5,267,982, 5,304,131 and 4,935,017. By inserting different shaped guide catheters through the outer guide catheter, different shapes for the distal end of the catheter are created. Inner and outer guide catheters are also disclosed, for example, in U.S. Pat. Nos. 5,304,131, 5,279,546, 5,120,323 and 4,810,244 and 5,290,229.
Atrial fibrillation is the most common sustained heart arrhythmia. It is estimated to occur in upwards of 0.4 percent of the adult population and perhaps as many as 10 percent of the population who are 60 years or older. Cox, J. L., et al., Electrophysiology, Pacing and Arrhythmia, "Operations for Atrial Fibrillation," Clin. Cardiol. 14, 827-834 (1991). Atrial arrhythmia may be transient or persistent. While most atrial arrhythmia occurs in individuals having other forms of underlying heart disease, some atrial arrhythmias occur independently. While atrial arrhythmias do not directly cause death as frequently as ventricular arrhythmias, they increase the risk factor for a number of other diseases such as strokes, thrombosis, atherosclerosis, systemic and cerebral embolism and cause a number of additional medical problems.
Another treatment for atrial arrhythmia or fibrillation involves the use of an implanted atrial defibrillator or cardioversion. See, for example, U.S. Pat. Nos. 5,282,836, 5,271,392 and 5,209,229. See also Martin, D., et al., Atrial Fibrillation, pp. 42-59 (1994).
Certain patients with symptomatic or life threatening atrial arrhythmias, however, cannot be adequately treated by drugs or these medical devices. Other forms of aggressive treatment are mandated, which may include surgery. For example, a surgical procedure for the treatment of atrial arrhythmia known as the "Maze" procedure is disclosed in Cox, J. L. et al., Electrophysiology, Pacing and Arrhythmia, "Operations for Atrial Fibrillation," Clin. Cardiol. 14, 827-834 (1991). See also Cox, J. L., et al., "The Surgical Treatment of Atrial Fibrillation," The Journal of Thoracic and Cardiovascular Surgery, Vol. 101, No. 4, pp. 584-592, 569-583 (April, 1991), and Cox, J. L., et al., "The Surgical Treatment of Atrial Fibrillation," The Journal of Thoracic and Cardiovascular Surgery, Vol. 101, No. 4, pp. 406-426 (March, 1991). Other surgical procedures for atrial arrhythmia are disclosed, for example, in Martin, D., et al., Atrial Fibrillation, pps. 54-56 (1994). Another procedure used for certain types of cardiac arrhythmia (but not atrial fibrillation) within the last 10 to 15 years is catheter ablation. This procedure has been used to interrupt or modify existing conduction pathways associated with ventricular arrhythmias within the heart. The particular area for ablation depends on the type of underlying ventricular arrhythmia. One common ablation procedure is for the treatment of atrioventricular (AV) nodal reentrant tachycardia. With this problem ablation of the fast or slow AV nodal pathways has become an accepted treatment. See Singer, I., et al., "Catheter Ablation for Arrhythmias" Clinical Manual of Electrophysiology, pp. 421-431 (1993); Falk, R. H., et al., Atrial Fibrillation Mechanisms in Management, pp. 359-374 (1992); Horowitz, L. N., Current Management of Arrhythmias, pp. 373-378 (1991); and Martin, D., et al., Atrial Fibrillation, pp. 42-59 (1994). The use of ablation catheters for ablating locations within the heart has also been disclosed, for example in U.S. Pat. Nos. 4,641,649, 5,263,493, 5,231,995, 5,228,442 and 5,281,217. However, none utilize a guiding introducer to guide the ablation catheter to a particular location within the heart.
Catheter ablation of accessory pathways associated with Wolfe-Parkinson-White syndrome using a long vascular sheath using both a transseptal and retrograde approach is discussed in Saul, J. P., et al. "Catheter Ablation of Accessory Atrioventricular Pathways in Young Patients: Use of long vascular sheaths, the transseptal approach and a retrograde left posterior parallel approach" Journal of the American College of Cardiology, Vol. 21, no. 3, pps. 571-583 (Mar. 1, 1993). See also Swartz, J. F. "Radiofrequency Endocardial Catheter Ablation of Accessory Atrioventricular Pathway Atrial Insertion Sites" Circulation, Vol. 87, no. 2, pps. 487-499 (February, 1993).
The sources of energy used for catheter ablation vary. Initially, high voltage, direct current (DC) ablation techniques were commonly used. However, because of problems associated with the use of DC current, radio frequency (R.F.) ablation has become a preferred source of energy for some ablation procedures. The use of RF energy for ablation has been disclosed, for example, in U.S. Pat. Nos. 4,945,912, 5,209,229, 5,281,218, 5,242,441, 5,246,438, 5,281,213 and 5,293,868. Other energy sources being considered for ablation of heart tissue include laser, ultrasound, microwave and direct current (low energy and fulgutronization). Also shown have been procedures where the temperature of the surrounding fluid about the catheterization probe is reduced.
In addition, the use of radio frequency ablation energy for the treatment of Wolfe-Parkinson-White syndrome in the left atrium by use of a transseptal sheath is disclosed in Swartz, J. F. et al. "Radiofrequency Endocardial Catheter Ablation of Accessory Atrioventricular Pathway Atrial Insertion Sites" Circulation 87:487-499 (1993). See also Tracey, C. N. "Radio Frequency Catheter Ablation of Ectopic Atrial Tachycardia Using Paced Activation Sequence Mapping" J. Am. Coll. Cardiol. 21:910-917 (1993).
Ablation of a precise location within the heart requires the precise placement of the ablation catheter within the heart. Precise positioning of the ablation catheter is especially difficult because of the physiology of the heart, particularly as the ablation procedures generally occur while the heart is beating. Commonly, the placement of the catheter is determined by a combination of electrophysiological guidance and fluoroscopy (placement of the catheter in relation to known features of the heart which are marked by radiopaque diagnostic catheters which are placed in or at known anatomical structures such as the coronary sinus, high right atrium and the right ventricle).
While these techniques have been useful for certain arrhythmias, catheter ablation for treatment of atrial fibrillation within the atria has not been disclosed. At best, procedures for ablation of the AV node or the His-Purkinje bundle have been disclosed, for example in U.S. Pat. No. 4,641,649 and Martin, D., et al., Atrial Fibrillation, p. 53 (1994).